1. Field of the Invention
The present invention relates to using electrochemistry for rapid identification of metal alloys which involves the transfer of electron charge across the metal-electrolyte interface. This electrochemical technique is performed by placing a measuring device directly in the electrical circuit creating the electrochemical process. Use of this technique arises from the relative ease of implementation requiring instrumentation that, today, is relatively inexpensive and can be automated.1 The instrumentation for this invention is comprised of a rectifier, a groundbed consisting of four (4) copper rods, power supply, three (3) copper/copper sulfate (Cu/CuSO4) reference electrodes, a data logger for storing the buried lead and copper service pipes electrochemical potentials. More specifically, the present invention relates to using the electrochemical potentials of lead versus copper/copper sulfate (Cu/CuSO4) reference electrode (−0.500 volts). In addition, the present invention relates to using the electrochemical potentials of copper versus copper/copper sulfate (Cu/CuSO4) reference electrode (−0.200 volts) which is utilized under field (actual, environmental or in situ) conditions in detecting and differentiating buried lead service pipes and buried copper pipes which are sometimes attached to the same water meter and cast iron water supply main.2 1 R. Winston Revie, Uhlig's Corrision Handbook, Wiley, New York, 2000, p. 1179.2 A. W. Peabody, Control of Pipeline Corrosion, NACE Press, Houston, Sec. Ed., 2001, p. 4, 301.
2. Prior Art
A major goal in the electrochemical field has long been to detect buried lead and buried copper service water mains in the field without disruption to neighborhood streets. The present technique that is used demands that the streets of busy cities and residential neighborhoods be dug up and the lead and copper service lines are visually identified. These lead and copper service lines are buried three (3) to five (5) feet underground.
The Environmental Protection Agency (EPA) has mandated to several cities within the United States that buried lead service pipes must be identified and replaced within the next five (5) years, in order to prevent lead contamination of the drinking water system. Federal guidelines have set an “action level” for drinking water to contain as much as 15 parts per billion (ppb) of lead. Too much lead in the human body can cause serious damage to the brain, kidneys, nervous system, and red blood cells. It is estimated that lead in drinking water contributes 10% to 20% of total lead exposure in young children. Young children and pregnant women are particularly vulnerable to lead poisoning.
These tight EPA standards require cities to replace underground lead pipes with copper pipes and to implement corrosion control procedures to make water less likely to dissolve lead from pipes and plumbing fixtures. There are about three (3) dozen water systems nationwide whose lead tests have exceeded the federal safety standard since the year 2000, according to data supplied by EPA. Tests in most of these homes have revealed that the high lead content of the drinking water is due to the buried lead service lines. These communities have replaced several of these lines with copper lines in a haphazard manner, which has created the problem of identifying and differentiating the buried lead lines from the copper service lines.
In addition, there are cases where repairs have been done to these underground lead service lines when they fail (leak) due to corrosion. These failed buried lead pipes are dug up, cut, and repaired with copper service lines joining the uncorroded section of the lead line. This presents a electrochemical galvanic corrosion cell which exacerbates the corrosion of the lead pipe and accelerates the amount of lead deposited in the drinking water.3 The locations of these electrochemical galvanic cells where the lead joins the copper must be identified and the lead portion replaced with copper. 3 A. W. Peabody, Control of Pipeline Corrosion, NACE Press, Houston, Sec. Ed., 2001, p. 310.
The fundamental relationship in galvanic corrosion is described by Kirchhoff's second law:Ec−Ea=IRe+IRm  (1)were are Re is the resistance of the ground the pipe is buried in, Rm is the resistance of the metallic portion of the galvanic cell, Ec is the polarized potential of the cathodic member (copper), Ea is the polarized potential of the anodic member (lead). Generally, Rm is very small and can be neglected, both Ea and Ec are functions of the galvanic current I; hence, the potential difference between the two (2) metals where there is a current flow through the ground, does not equal the open circuit potential.4 4 R. Winston Revie, Uhlig's Corrosion Handbook, Wiley, New York, 2000, p. 153.
The identification of these lead and copper service mains is extremely important from a health aspect as well as the aesthetic and economical requirements of local governments. This present invention will remove buried lead service lines from the water system. Effectively removing the lead service lines will eliminate the lead content in the drinking water, consequently, improving the health of the population. Another advantage of this invention is that it eliminates the need to dig up the streets and neighborhoods which maintains the existing beauty and condition of the neighborhood. There is a very large economic impact, in that, the savings to local governments would be 80% of their present costs.
Presently, there is no electrochemical method available that would detect and differentiate buried lead and buried copper service water lines without digging up and disrupting a neighborhood. This electrochemical method allows for the identification and differentiation of buried lead and copper service water lines without any disruptions to the neighborhood and no digging up of the buried pipes.